In a Long Term Evolution (LTE) system of the 3rd Generation Partnership Project (3GPP), each user equipment (UE) uses a single-carrier frequency division multiple access transmission technology in an uplink direction. To ensure orthogonality between uplink signals of UEs, the uplink signals of the UEs need to arrive at a receive end of a base station at a same time, that is, uplink synchronization is needed.
The UE may ensure uplink synchronization by using a random access process. In the random access process, the UE sends a random access preamble to the base station. After receiving and detecting the random access preamble, the base station sends a random access response to the UE. The random access response includes a timing advance command, so that the UE performs transmission timing adjustment according to the timing advance command. The UE adjusts uplink transmission timing of a physical uplink control channel (PUCCH), a physical uplink shared channel (PUSCH), and a sounding reference signal (SRS) according to the timing advance command.
With development of a self-organizing network (SON), the transmission timing adjustment may further be applied to network planning and optimization. For example, the base station may analyze signal quality and UE distribution in different areas according to information reported by the UEs in measurement reports and according to timing advance (TA) information of the UEs, thereby learning information about coverage and traffic of a station, and determining whether a macro base station or a micro base station needs to be added to an area with poor coverage or high traffic or whether an antenna angle of the station needs to be adjusted. However, a current transmission timing adjustment mechanism has an adverse impact on accuracy of network planning and optimization.